Compliant printed flexible circuit

ABSTRACT

A compliant printed flexible circuit including a flexible polymeric film and at least one dielectric layer bonded to the polymeric film with recesses corresponding to a target circuit geometry. A conductive material is printed in at least a portion of the recesses to form a circuit geometry. At least one dielectric covering layer is printed over at least the circuit geometry. Openings can be printed in the dielectric covering layer to provide access to at least a portion of the circuit geometry.

TECHNICAL FIELD

The present application relates to a high performance compliant printedflexible circuit that merges the long-term performance advantages offlexible circuits, with the flexibility of additive printing technology.

BACKGROUND OF THE INVENTION

Traditional printed circuits are often constructed in what is commonlycalled rigid or flexible formats. The rigid versions are used in nearlyevery electronic system, where the printed circuit board (PCB) isessentially a laminate of materials and circuits that when built isrelatively stiff or rigid and cannot be bent significantly withoutdamage.

Flexible circuits have become very popular in many applications wherethe ability to bend the circuit to connect one member of a system toanother has some benefit. These flexible circuits are made in a verysimilar fashion as rigid PCB's, where layers of circuitry and dielectricmaterials are laminated. The main difference is the material set usedfor construction. Typical flexible circuits start with a polymer filmthat is clad, laminated, or deposited with copper. A photolithographyimage with the desired circuitry geometry is printed onto the copper,and the polymer film is etched to remove the unwanted copper. Flexiblecircuits are very commonly used in many electronic systems such asnotebook computers, medical devices, displays, handheld devices, autos,aircraft and many others.

Flexible circuits are processed similar to that of rigid PCB's with aseries of imaging, masking, drilling, via creation, plating, andtrimming steps. The resulting circuit can be bent, without damaging thecopper circuitry. Flexible circuits are solderable, and can have devicesattached to provide some desired function. The materials used to makeflexible circuits can be used in high frequency applications where thematerial set and design features can often provide better electricalperformance than a comparable rigid circuit.

Flexible circuits are connected to electrical system in a variety ofways. In most cases, a portion of the circuitry is exposed to create aconnection point. Once exposed, the circuitry can be connected toanother circuit or component by soldering, conductive adhesive,thermosonic welding, pressure or a mechanical connector. In general, theterminals are located on an end of the flexible circuit, where edgetraces are exposed or in some cases an area array of terminals areexposed. Often there is some sort of mechanical enhancement at or nearthe connection to prevent the joints from being disconnected during useor flexure.

In general, flexible circuits are expensive compared to some rigid PCBproducts. Flexible circuits also have some limitations regarding layercount or feature registration, and are therefore generally only used forsmall or elongated applications.

BRIEF SUMMARY OF THE INVENTION

The present disclosure is directed to a high performance compliantprinted flexible circuit (“CFPC”) that will enable next generationelectrical performance. The present disclosure merges the long-termperformance advantages of flexible circuits, with the flexibility ofadditive printing technology.

This present compliant printed flexible circuit enables internal and/orexternal compliance to enhance the mechanical performance of thecircuit. Electrical devices can be printed on the CFPC, such as forexample, ground planes, power planes, transistors, capacitors,resistors, RF antennae, shielding, filters, signal or power altering andenhancing devices, memory devices, embedded IC, and the like.

The present CFPC can be produced digitally, without tooling or costlyartwork. The CFPC can be produced as a “Green” product, with dramaticreductions in environmental issues related to the production ofconventional flexible circuits.

Contact members can be printed in a variety of shapes and sizes,depending on the terminal structure on the circuit members. The contactmembers can be positioned at a variety of locations, heights, or spacingto match the parameters of existing connections, allowing replacement ofexisting interconnect connectors, without changing hardware or the PCB.In some embodiments, the tips of the contact members are treated withspecialty materials to increase long term reliability, such as for atest socket application.

The use of additive printing processes permits the material set in agiven layer to vary. Traditional PCB and flex circuit fabricationmethods take sheets of material and stack them up, laminate, and/ordrill. The materials in each layer are limited to the materials in aparticular sheet. Additive printing technologies permit a wide varietyof materials to be applied on a layer with a registration relative tothe features of the previous layer. Selective addition of conductive,non-conductive, or semi-conductive materials at precise locations tocreate a desired effect has the major advantages in tuning impedance oradding electrical function on a given layer. Tuning performance on alayer by layer basis relative to the previous layer greatly enhanceselectrical performance.

Since the individual contact members are preferably printed, the presentCFPC can be removed and replaced without having to handle or assembleindividual contact members. The circuit members on the CFPC can beconfigured to mate with existing or custom connectors in a LIF, ZIF, orplugged connector configuration, while maintaining or improving signalintegrity.

One embodiment is directed to a compliant printed flexible circuitincluding a flexible polymeric film and at least one dielectric layerbonded to the polymeric film with recesses corresponding to a targetcircuit geometry. A conductive material is printed in at least a portionof the recesses to form a circuit geometry. At least one dielectriccovering layer is printed over at least the circuit geometry. At leastone opening in the dielectric covering layer provides access to at leasta portion of the circuit geometry.

A conductive plating layer is optionally applied on at least a portionof the circuit geometry. The conductive material can be sinteredconductive particles or a conductive ink. In one embodiment, a compliantmaterial is located between the polymeric film and at least a portion ofthe circuit geometry. The compliant material is preferably aligned withthe opening in the dielectric layer.

The resulting circuit geometry preferably has conductive traces thathave substantially rectangular cross-sectional shapes, corresponding tothe recesses. The use of additive printing processes permit conductivematerial, non-conductive material, and semi-conductive material to belocated on a single layer.

In one embodiment, pre-formed conductive trace materials are located inthe recesses. The recesses are than plated to form conductive traceswith substantially rectangular cross-sectional shapes. In anotherembodiment, a conductive foil is pressed into at least a portion of therecesses. The conductive foil is sheared along edges of the recesses.The excess conductive foil not located in the recesses is removed andthe recesses are plated to form conductive traces with substantiallyrectangular cross-sectional shapes.

At least one electrical device is optionally printed on a dielectriclayer or the polymeric film and electrically coupled to at least aportion of the circuit geometry. Optical quality materials can beprinted or deposited in at least a portion of the recesses to formoptical circuit geometries. Alternatively, optical fibers can be locatedin the recesses.

Vias can be printed on the compliant printed flexible circuit toelectrically couple adjacent layers of the circuit geometry. One or morecontact members electrically coupled to at least a portion of thecircuit geometry are printed to extend above the dielectric coveringlayer. The compliant printed flexible circuit is optionally singulatedadjacent at least one of the contact members.

In one embodiment, at least one contact member extends along a firstsurface of the compliant printed flexible circuit and at least oneprinted compliant member is located on a second surface of the compliantprinted flexible circuit opposite at least one of the contact members.

The present disclosure is also directed to an edge connector on thecompliant printed flexible circuit. A first portion of the circuitgeometry extends beyond the dielectric covering layer. A compliantmaterial is located along a surface of the first portion of the circuitgeometry. A second portion of the circuit geometry is located on top ofthe compliant material.

The present disclosure is also directed to an electrical interconnectassembly. A housing retains the compliant printed flexible circuit.Electrical contacts on a first circuit member are compressively engagedwith contact members located along a first surface of the compliantprinted flexible circuit. Electrical contacts on a second circuit memberare compressively engaged with contact members located along a secondsurface of the compliant printed flexible circuit. The first and secondcircuit members are selected from one of a dielectric layer, a printedcircuit board, a flexible circuit, a bare die device, an integratedcircuit device, organic or inorganic substrates, or a rigid circuit.

The present disclosure is also directed to a method of making acompliant printed flexible circuit. At least one dielectric layer isbonded to a flexible polymeric film to create recesses corresponding toa target circuit geometry. A conductive material is printed in at leasta portion of the recesses to form a circuit geometry. At least onedielectric covering layer is printed over at least the circuit geometry.

The dielectric covering layer can be printed with at least one openingthat provides access to at least a portion of the circuit geometry. Theconductive material is preferably plated. The conductive material,compliant materials, electrical devices, optical quality material, andthe contact members are all preferably printed.

The present disclosure is also directed to a method of making an edgeconnector for a compliant printed flexible circuit. A first portion ofthe circuit geometry is printed beyond the dielectric covering layer. Acompliant material is printed along a surface of the first portion ofthe circuit geometry. A second portion of the circuit geometry isprinted on top of the compliant material.

The present disclosure is also directed to a method of making anelectrical interconnect assembly. A compliant printed flexible circuitis retained in a housing. Electrical contacts on a first circuit memberare compressively coupled with contact members located along a firstsurface of the compliant printed flexible circuit, and electricalcontacts on a second circuit member are compressively coupled withcontact members located along a second surface of the compliant printedflexible circuit.

The present disclosure is also directed to several additive processesthat combine the mechanical or structural properties of a polymermaterial, while adding metal materials in an unconventional fashion, tocreate electrical paths that are refined to provide electricalperformance improvements. By adding or arranging metallic particles,conductive inks, plating, or portions of traditional alloys, thecompliant printed flexible circuit reduces parasitic electrical effectsand impedance mismatch, potentially increasing the current carryingcapacity.

The present compliant printed flexible circuit can serve as a platformto add passive and active circuit features to improve electricalperformance or internal function and intelligence. For example,electrical features and devices are printed onto the interconnectassembly using, for example, inkjet printing technology or otherprinting technologies. The ability to enhance the compliant printedflexible circuit, such that it mimics aspects of an IC package and aPCB, allows for reductions in complexity for the IC package and the PCB,while improving the overall performance of the interconnect assembly.

The printing process permits the fabrication of functional structures,such as conductive paths and electrical devices, without the use ofmasks or resists. Features down to about 10 microns can be directlywritten in a wide variety of functional inks, including metals,ceramics, polymers and adhesives, on virtually any substrate—silicon,glass, polymers, metals and ceramics. The substrates can be planar andnon-planar surfaces. The printing process is typically followed by athermal treatment, such as in a furnace or with a laser, to achievedense functionalized structures.

The compliant printed flexible circuit can be configured with conductivetraces that reduce or redistribute the terminal pitch, without theaddition of an interposer or daughter substrate. Grounding schemes,shielding, electrical devices, and power planes can be added to theinterconnect assembly, reducing the number of connections to the PCB andrelieving routing constraints while increasing performance.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a cross-sectional view of a method of making a compliantprinted flexible circuit in accordance with an embodiment of the presentdisclosure.

FIG. 2 illustrates a printed circuit geometry on the compliant printedflexible circuit of FIG. 1.

FIG. 3 illustrates the compliant printed flexible circuit of FIG. 1.

FIG. 4 illustrates a compliant printed flexible circuit with printedcompliant features in accordance with an embodiment of the presentdisclosure.

FIG. 5 illustrates a compliant printed flexible circuit with opticalfeatures in accordance with an embodiment of the present disclosure.

FIG. 6 illustrates an alternate compliant printed flexible circuit withoptical features in accordance with an embodiment of the presentdisclosure.

FIG. 7 illustrates an alternate compliant printed flexible circuit withprinted vias in accordance with an embodiment of the present disclosure.

FIG. 8 illustrates an alternate compliant printed flexible circuit withprinted electrical devices in accordance with an embodiment of thepresent disclosure.

FIG. 9 illustrates an alternate compliant printed flexible circuit withprinted compliant electrical pads to plug into another connector inaccordance with an embodiment of the present disclosure.

FIG. 10 illustrates a method of making a compliant printed flexiblecircuit in accordance with an embodiment of the present disclosure.

FIGS. 11 and 12 illustrate other aspects of the method of FIG. 10.

FIG. 13 illustrates a compliant printed flexible circuit made inaccordance with the method of FIGS. 10, 11 and 12.

FIG. 14 illustrates a compliant printed flexible circuit incorporatedinto a socket assembly in accordance with an embodiment of the presentdisclosure.

FIG. 15 illustrates an alternate compliant printed flexible circuit inaccordance with an embodiment of the present disclosure.

FIG. 16 illustrates an alternate compliant printed flexible circuit inaccordance with an embodiment of the present disclosure.

FIG. 17 illustrates an alternate compliant printed flexible circuit inaccordance with an embodiment of the present disclosure.

FIG. 18 illustrates an alternate compliant printed flexible circuit inaccordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

A complaint printed flexible circuit according to the present disclosuremay permit fine contact-to-contact spacing (pitch) on the order of lessthan 1.0 mm pitch, and more preferably a pitch of less than about 0.7millimeter, and most preferably a pitch of less than about 0.4millimeter. Such fine pitch compliant printed flexible circuits areespecially useful for communications, wireless, and memory devices.

The present compliant printed flexible circuit can be configured as alow cost, high signal performance interconnect assembly, which has a lowprofile that is particularly useful for desktop and mobile PCapplications. IC devices to be installed and uninstalled without theneed to reflow solder. The solder-free electrical connection of the ICdevices is environmentally friendly.

FIG. 1 is a side cross-sectional view of a method for replicating aflexible circuit member using additive processes in accordance with anembodiment of the present disclosure. Flexible polymeric film 50includes one or more dielectric layers 52, 54 configured to includerecesses 56 corresponding to a desired circuit geometry. In oneembodiment, the dielectric layers 52, 54 are printed or placed onsurface 58 of the flexible polymeric film 50. The recesses 56 can bedefined by printing, embossing, imprinting, chemical etching with aprinted mask, or a variety of other techniques. A number of differentmaterials are used as the flexible polymeric film 50 including:polyester (PET), polyimide (PI), polyethylene napthalate (PEN),Polyetherimide (PEI), along with various fluoropolymers (FEP) andcopolymers. Polyimide films are the most prevalent due to theiradvantageous electrical, mechanical, chemical, and thermal properties.

As illustrated in FIG. 2, a metalizing layer is deposited in therecesses 56 to create circuit geometry 62. Metalizing can be performedby printing conductive particles followed by a sintering step, byprinting conductive inks, or a variety of other techniques. Theresulting metalized layer is preferably plated to improve conductiveproperties. The circuit geometry 62 is preferably of copper or similarmetallic materials such as phosphor bronze or beryllium-copper. Theplating is preferably a corrosion resistant metallic material such asnickel, gold, silver, palladium, or multiple layers thereof.

As illustrated in FIG. 3, another dielectric or insulating layer 64 isapplied to the circuit geometry 62 and the dielectric layer 54. Thenature of the printing process allows for selective application ofdielectric layer 64 to leave selected portions 66 of the circuitgeometry 62 expose if desired. The resulting compliant printed flexiblecircuit 68 can potentially be considered entirely “green” with limitedor no chemistry used to produce beyond the direct write materials.

The recesses 56 in the layers 52, 54, 64 permit control of the location,cross section, material content, and aspect ratio of the conductivetraces in the circuit geometry 62. Maintaining the conductive traceswith a cross-section of 1:1 or greater provides greater signal integritythan traditional subtractive trace forming technologies. For example,traditional methods take a sheet of a given thickness and etches thematerial between the traces away to have a resultant trace that isusually wider than it is thick. The etching process also removes morematerial at the top surface of the trace than at the bottom, leaving atrace with a trapezoidal cross-sectional shape, degrading signalintegrity in some applications. Using the recesses 56 to control theaspect ratio of the conductive traces results in a more rectangular orsquare cross-section of the conductive traces in the circuit geometry62, with the corresponding improvement in signal integrity.

In another embodiment, pre-patterned or pre-etched thin conductive foilcircuit traces are transferred to the recesses 56. For example, apressure sensitive adhesive can be used to retain the copper foilcircuit traces in the recesses 56. The trapezoidal cross-sections of thepre-formed conductive foil traces are then post-plated. The platingmaterial fills the open spaces in the recesses 56 not occupied by thefoil circuit geometry, resulting in a substantially rectangular orsquare cross-sectional shape corresponding to the shape of the recesses56.

In another embodiment, a thin conductive foil is pressed into therecesses 56, and the edges of the recesses 56 acts to cut or shear theconductive foil. The process locates a portion of the conductive foil inthe trenches 56, but leaves the negative pattern of the conductive foilnot wanted outside and above the trenches 56 for easy removal. Again,the foil in the trenches 56 is preferably post plated to add material toincrease the thickness of the conductive traces in the circuit geometry62 and to fill any voids left between the conductive foil and therecesses 56.

The dielectric layers 52, 54, 64 may be constructed of any of a numberof dielectric materials that are currently used to make sockets,semiconductor packaging, and printed circuit boards. Examples mayinclude UV stabilized tetrafunctional epoxy resin systems referred to asFlame Retardant 4 (FR-4); bismaleimide-triazine thermoset epoxy resinsreferred to as BT-Epoxy or BT Resin; and liquid crystal polymers (LCPs),which are polyester polymers that are extremely unreactive, inert andresistant to fire. Other suitable plastics include phenolics,polyesters, and Ryton® available from Phillips Petroleum Company.

In one embodiment, one or more of the layer 52, 54, 64 are designed toprovide electrostatic dissipation or to reduce cross-talk between thetraces of the circuit geometry 62. An efficient way to preventelectrostatic discharge (“ESD”) is to construct one of the layers frommaterials that are not too conductive but that will slowly conductstatic charges away. These materials preferably have resistivity valuesin the range of 10⁵ to 10¹¹ Ohm-meters.

FIG. 4 illustrates an alternate compliant printed flexible circuit 80 inaccordance with an embodiment of the present disclosure. Dielectriclayer 82 includes openings 84 into which compliant material 86 isprinted before formation of circuit geometry 88. The compliant printedmaterial 86 improves reliability during flexure of exposed portion 90the circuit geometry 88.

FIG. 5 illustrates an alternate compliant printed flexible circuit 100in accordance with an embodiment of the present disclosure. Opticalfibers 102 are located between layers 104, 106 of dielectric material.In one embodiment, optical fibers 102 is positioned over printedcompliant layer 108, and dielectric layer 110 is printed over and aroundthe optical fibers 102. A compliant layer 112 is preferably printedabove the optical fiber 102 as well. The compliant layers 108, 112support the optical fibers 102 during flexure. In another embodiment,the dielectric layer 110 is formed or printed with recesses into whichthe optical fibers 102 are deposited.

In another embodiment, optical quality materials 114 are printed duringprinting of the compliant printed flexible circuit 100. The opticalquality material 114 and/or the optical fibers 102 comprise opticalcircuit geometries. The printing process allows for deposition ofcoatings in-situ that enhance the optical transmission or reduce loss.The precision of the printing process reduces misalignment issues whenthe optical materials 114 are optically coupled with another opticalstructure.

FIG. 6 illustrates another embodiment of a present compliant printedflexible circuit 140 in accordance with an embodiment of the presentdisclosure. Embedded coaxial RF circuits 142 or printed micro strip RFcircuits 144 are located with dielectric/metal layers 146. These RFcircuits 142, 144 are preferably created by printing dielectrics andmetallization geometry.

As illustrated in FIG. 7, use of additive processes allows the creationof a compliant printed flexible circuit 160 with inter-circuit, 3Dlattice structures 162 having intricate routing schemes. Vias 164 can beprinted with each layer, without drilling.

FIG. 8 illustrates a compliant printed flexible circuit 180 with printedelectrical devices 182. The electrical devices 182 can include passiveor active functional elements. Passive structure refers to a structurehaving a desired electrical, magnetic, or other property, including butnot limited to a conductor, resistor, capacitor, inductor, insulator,dielectric, suppressor, filter, varistor, ferromagnet, and the like. Inthe illustrated embodiment, electrical devices 182 include printed LEDindicator 184 and display electronics 186. Geometries can also beprinted to provide capacitive coupling 188.

The electrical devices 182 are preferably printed during construction ofthe interconnect assembly 100. The electrical devices 182 can be groundplanes, power planes, electrical connections to other circuit members,dielectric layers, conductive traces, transistors, capacitors,resistors, RF antennae, shielding, filters, signal or power altering andenhancing devices, memory devices, embedded IC, and the like. Forexample, the electrical devices 182 can be formed using printingtechnology, adding intelligence to the compliant printed flexiblecircuit 180. Features that are typically located on other circuitmembers can be incorporated into the flexible circuit 180 in accordancewith an embodiment of the present disclosure.

The availability of printable silicon inks provides the ability to printelectrical devices 90, 92, such as disclosed in U.S. Pat. Nos. 7,485,345(Renn et al.); 7,382,363 (Albert et al.); 7,148,128 (Jacobson);6,967,640 (Albert et al.); 6,825,829 (Albert et al.); 6,750,473(Amundson et al.); 6,652,075 (Jacobson); 6,639,578 (Comiskey et al.);6,545,291 (Amundson et al.); 6,521,489 (Duthaler et al.); 6,459,418(Comiskey et al.); 6,422,687 (Jacobson); 6,413,790 (Duthaler et al.);6,312,971 (Amundson et al.); 6,252,564 (Albert et al.); 6,177,921(Comiskey et al.); 6,120,588 (Jacobson); 6,118,426 (Albert et al.); andU.S. Pat. Publication No. 2008/0008822 (Kowalski et al.), which arehereby incorporated by reference. In particular, U.S. Pat. Nos.6,506,438 (Duthaler et al.) and 6,750,473 (Amundson et al.), which areincorporated by reference, teach using ink-jet printing to make variouselectrical devices, such as, resistors, capacitors, diodes, inductors(or elements which may be used in radio applications or magnetic orelectric field transmission of power or data), semiconductor logicelements, electro-optical elements, transistor (including, lightemitting, light sensing or solar cell elements, field effect transistor,top gate structures), and the like.

The electrical devices 202 can also be created by aerosol printing, suchas disclosed in U.S. Pat. Nos. 7,674,671 (Renn et al.); 7,658,163 (Rennet al.); 7,485,345 (Renn et al.); 7,045,015 (Renn et al.); and 6,823,124(Renn et al.), which are hereby incorporated by reference.

Printing processes are preferably used to fabricate various functionalstructures, such as conductive paths and electrical devices, without theuse of masks or resists. Features down to about 10 microns can bedirectly written in a wide variety of functional inks, including metals,ceramics, polymers and adhesives, on virtually any substrate—silicon,glass, polymers, metals and ceramics. The substrates can be planar andnon-planar surfaces. The printing process is typically followed by athermal treatment, such as in a furnace or with a laser, to achievedense functionalized structures.

Ink jet printing of electronically active inks can be done on a largeclass of substrates, without the requirements of standard vacuumprocessing or etching. The inks may incorporate mechanical, electricalor other properties, such as, conducting, insulating, resistive,magnetic, semi conductive, light modulating, piezoelectric, spin,optoelectronic, thermoelectric or radio frequency.

A plurality of ink drops are dispensed from the print head directly to asubstrate or on an intermediate transfer member. The transfer member canbe a planar or non-planar structure, such as a drum. The surface of thetransfer member can be coated with a non-sticking layer, such assilicone, silicone rubber, or Teflon.

The ink (also referred to as function inks) can include conductivematerials, semi-conductive materials (e.g., p-type and n-typesemiconducting materials), metallic material, insulating materials,and/or release materials. The ink pattern can be deposited in preciselocations on a substrate to create fine lines having a width smallerthan 10 microns, with precisely controlled spaces between the lines. Forexample, the ink drops form an ink pattern corresponding to portions ofa transistor, such as a source electrode, a drain electrode, adielectric layer, a semiconductor layer, or a gate electrode.

The substrate can be an insulating polymer, such as polyethyleneterephthalate (PET), polyester, polyethersulphone (PES), polyimide film(e.g. Kapton, available from DuPont located in Wilmington, Del.; Upilexavailable from Ube Corporation located in Japan), or polycarbonate.Alternatively, the substrate can be made of an insulator such as undopedsilicon, glass, or a plastic material. The substrate can also bepatterned to serve as an electrode. The substrate can further be a metalfoil insulated from the gate electrode by a non-conducting material. Thesubstrate can also be a woven material or paper, planarized or otherwisemodified on at least one surface by a polymeric or other coating toaccept the other structures.

Electrodes can be printed with metals, such as aluminum or gold, orconductive polymers, such as polythiophene or polyaniline. Theelectrodes may also include a printed conductor, such as a polymer filmcomprising metal particles, such as silver or nickel, a printedconductor comprising a polymer film containing graphite or some otherconductive carbon material, or a conductive oxide such as tin oxide orindium tin oxide.

Dielectric layers can be printed with a silicon dioxide layer, aninsulating polymer, such as polyimide and its derivatives, poly-vinylphenol, polymethylmethacrylate, polyvinyldenedifluoride, an inorganicoxide, such as metal oxide, an inorganic nitride such as siliconnitride, or an inorganic/organic composite material such as anorganic-substituted silicon oxide, or a sol-gel organosilicon glass.Dielectric layers can also include a bicylcobutene derivative (BCB)available from Dow Chemical (Midland, Mich.), spin-on glass, ordispersions of dielectric colloid materials in a binder or solvent.

Semiconductor layers can be printed with polymeric semiconductors, suchas, polythiophene, poly(3-alkyl)thiophenes, alkyl-substitutedoligothiophene, polythienylenevinylene, poly(para-phenylenevinylene) anddoped versions of these polymers. An example of suitable oligomericsemiconductor is alpha-hexathienylene. Horowitz, Organic Field-EffectTransistors, Adv. Mater., 10, No. 5, p. 365 (1998) describes the use ofunsubstituted and alkyl-substituted oligothiophenes in transistors. Afield effect transistor made with regioregular poly(3-hexylthiophene) asthe semiconductor layer is described in Bao et al., Soluble andProcessable Regioregular Poly(3-hexylthiophene) for Thin FilmField-Effect Transistor Applications with High Mobility, Appl. Phys.Lett. 69 (26), p. 4108 (December 1996). A field effect transistor madewith a-hexathienylene is described in U.S. Pat. No. 5,659,181, which isincorporated herein by reference.

A protective layer can optionally be printed onto the electricaldevices. The protective layer can be an aluminum film, a metal oxidecoating, a polymeric film, or a combination thereof.

Organic semiconductors can be printed using suitable carbon-basedcompounds, such as, pentacene, phthalocyanine, benzodithiophene,buckminsterfullerene or other fullerene derivatives,tetracyanonaphthoquinone, and tetrakisimethylanimoethylene. Thematerials provided above for forming the substrate, the dielectriclayer, the electrodes, or the semiconductor layer are exemplary only.Other suitable materials known to those skilled in the art havingproperties similar to those described above can be used in accordancewith the present disclosure.

The ink-jet print head preferably includes a plurality of orifices fordispensing one or more fluids onto a desired media, such as for example,a conducting fluid solution, a semiconducting fluid solution, aninsulating fluid solution, and a precursor material to facilitatesubsequent deposition. The precursor material can be surface activeagents, such as octadecyltrichlorosilane (OTS).

Alternatively, a separate print head is used for each fluid solution.The print head nozzles can be held at different potentials to aid inatomization and imparting a charge to the droplets, such as disclosed inU.S. Pat. No. 7,148,128 (Jacobson), which is hereby incorporated byreference. Alternate print heads are disclosed in U.S. Pat. No.6,626,526 (Ueki et al.), and U.S. Pat. Publication Nos. 2006/0044357(Andersen et al.) and 2009/0061089 (King et al.), which are herebyincorporated by reference.

The print head preferably uses a pulse-on-demand method, and can employone of the following methods to dispense the ink drops: piezoelectric,magnetostrictive, electromechanical, electro pneumatic, electrostatic,rapid ink heating, magneto hydrodynamic, or any other technique wellknown to those skilled in the art. The deposited ink patterns typicallyundergo a curing step or another processing step before subsequentlayers are applied.

While ink jet printing is preferred, the term “printing” is intended toinclude all forms of printing and coating, including: pre-meteredcoating such as patch die coating, slot or extrusion coating, slide orcascade coating, and curtain coating; roll coating such as knife overroll coating, forward and reverse roll coating; gravure coating; dipcoating; spray coating; meniscus coating; spin coating; brush coating;air knife coating; screen printing processes; electrostatic printingprocesses; thermal printing processes; and other similar techniques.

FIG. 9 illustrates an alternate compliant printed flexible circuit 200with printed compliant material 202 added between circuit geometries204, 206 to facilitate insertion of exposed circuit geometries 208, 210into a receptacle or socket. The compliant material 202 can supplementor replace the compliance in the receptacle or socket. In oneembodiment, the compliance is provided by a combination of the compliantmaterial 202 and the exposed circuit geometries 208, 210.

FIG. 10 is a side sectional view of a method of making a compliantprinted flexible circuit 250 in accordance with an embodiment of thepresent disclosure. Polymeric film 252 includes a plurality of cavities254 extending through dielectric layer 256. The cavities 254 can beformed using a variety of techniques, such as molding, machining,printing, imprinting, embossing, etching, coining, and the like.Although the cavities 254 are illustrated as truncated cones orpyramids, a variety of other shapes can be used, such as for example,cones, hemispherical shapes, and the like.

As illustrated in FIG. 11, metalizing layer is printed in the cavities254 to create contact member 258, as discussed above. As illustrated inFIG. 12, a compliant layer 260 is printed on the dielectric layer 256,followed by dielectric layer 262 establishing circuit geometry.

FIG. 13 illustrates circuit geometries 264 printed as discussed above.In one embodiment, the circuit geometries 264 are formed by depositing aconductive material in a first state in the recesses, and then processedto create a second more permanent state. For example, the metallicpowder is printed according to the circuit geometry and subsequentlysintered, or the curable conductive material flows into the circuitgeometry and is subsequently cured. As used herein “cure” andinflections thereof refers to a chemical-physical transformation thatallows a material to progress from a first form (e.g., flowable form) toa more permanent second form. “Curable” refers to an uncured materialhaving the potential to be cured, such as for example by the applicationof a suitable energy source.

Second compliant layer 270 is printed on exposed surfaces 272 of thedielectric layers 262 and circuit geometries 264. The second compliantlayer 270 and second dielectric layer 274 are selectively printed topermit printing of contact member 276. Alternatively, pre-fabricatedcontact members 276 can be bonded to the circuit geometries 264. As usedherein, “bond” or “bonding” refers to, for example, adhesive bonding,solvent bonding, ultrasonic welding, thermal bonding, or any othertechniques suitable for attaching adjacent layers to a substrate.

The dielectric layer 274 adjacent contact members 276 is optionallysingulated to permit greater compliance. As used herein, “singulated”refers to slits, cuts, depressions, perforations, and/or points ofweakness. In another embodiment, the compliant printed flexible circuit250 is made in two portions and then bonded together.

FIG. 14 illustrates a socket assembly 300 incorporating the compliantprinted flexible circuit 250 of FIG. 13, in accordance with anembodiment of the present disclosure. The dielectric layer 256 isseparated from the polymeric film 252 to expose contact member 258. Inthe illustrated embodiment, the dielectric layer 274 is bonded tosurface 302 of socket housing 304 so that contact members 276 arepositioned in recess 306. First circuit member 308, such as an ICdevice, is positioned in the recess 306 so that the terminals 310 alignwith the contact members 276.

The contact members 258, 276 are optionally plated, either before orafter the compliant printed flexible circuit 250 is installed in thesocket housing 304. In another embodiment, the contact members 258, 276are deformed, such as for example by coining or etching, to facilitateengagement with terminals 310 on the first circuit member 308 and/orterminal 312 on second circuit member 314.

In operation, the first circuit member 308, socket assembly 300 and thesecond circuit member 314 are compressively coupled so that contactmember 276 electrically couples with terminal 310 and contact member 258electrically couples with contact pad 312. Compliant layer 260 biasesthe contact member 276 into engagement with the terminal 310, while thecompliant layer 270 biases the contact member 258 into engagement withthe pad 312. The compliant layers 260, 270 also permit the contactmembers 276, 258 to deflect and compensate for non-planarity of theterminals 310 or the pads 312. As used herein, the term “circuitmembers” refers to, for example, a packaged integrated circuit device,an unpackaged integrated circuit device, a printed circuit board, aflexible circuit, a bare-die device, an organic or inorganic substrate,a rigid circuit, or any other device capable of carrying electricalcurrent.

FIG. 15 illustrates a compliant printed flexible circuit 330 withcompliant structure 332 printed to add compliance and normal force 334external to the circuit geometry 336. For example, the compliantstructure 332 can be a printed/sintering metallic spring. In anotherembodiment, the compliant structure 332 is a stamped or etched metallic,plastic, or overmolded leadframe that is added to the compliant printedflexible circuit 330. The compliant members 332 can optionally besingulated in tandem with the circuit geometry 336 to allow forindividual contact compliance.

FIG. 16 illustrates a compliant printed flexible circuit 350 with malecontact member 352 in accordance with an embodiment of the presentdisclosure. Contact member 352 is preferably inserted through opening354 printed in dielectric layers 356, 358 and circuit geometry 360. Theresiliency of the dielectric layers 356, 358 permits plastic deformationto permit enlarged end 362 to penetrate the opening 354 in the compliantprinted flexible circuit 350. The resilience of the dielectric layers356, 358 also permit the contact member 360 to move in all six degreesof freedom (X-Y-Z-Pitch-Roll-Yaw) to facilitate electrical coupling withfirst and second circuit members 364, 366.

FIG. 17 illustrates a compliant printed flexible circuit 370 withprinted compliant member 372 located above contact member 374 inaccordance with an embodiment of the present disclosure. The printedcompliant member 372 and associated contact member 374 is preferablysingulated to promote flexure and compliance.

FIG. 18 illustrates an alternate embodiment of a compliant printedflexible circuit 380 where printed compliant member 382 is located oncircuit member 384. In the illustrated embodiment, secondary printedcompliant member 386 is located on the compliant printed flexiblecircuit 380 above contact member 388.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range is encompassed within the embodiments of the disclosure.The upper and lower limits of these smaller ranges which mayindependently be included in the smaller ranges is also encompassedwithin the embodiments of the disclosure, subject to any specificallyexcluded limit in the stated range. Where the stated range includes oneor both of the limits, ranges excluding either both of those includedlimits are also included in the embodiments of the present disclosure.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the embodiments of the present disclosure belong.Although any methods and materials similar or equivalent to thosedescribed herein can also be used in the practice or testing of theembodiments of the present disclosure, the preferred methods andmaterials are now described. All patents and publications mentionedherein, including those cited in the Background of the application, arehereby incorporated by reference to disclose and described the methodsand/or materials in connection with which the publications are cited.

The publications discussed herein are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present disclosure isnot entitled to antedate such publication by virtue of prior invention.Further, the dates of publication provided may be different from theactual publication dates which may need to be independently confirmed.

Other embodiments of the disclosure are possible. Although thedescription above contains much specificity, these should not beconstrued as limiting the scope of the disclosure, but as merelyproviding illustrations of some of the presently preferred embodimentsof this disclosure. It is also contemplated that various combinations orsub-combinations of the specific features and aspects of the embodimentsmay be made and still fall within the scope of the present disclosure.It should be understood that various features and aspects of thedisclosed embodiments can be combined with or substituted for oneanother in order to form varying modes of the disclosed embodiments ofthe disclosure. Thus, it is intended that the scope of the presentdisclosure herein disclosed should not be limited by the particulardisclosed embodiments described above.

Thus the scope of this disclosure should be determined by the appendedclaims and their legal equivalents. Therefore, it will be appreciatedthat the scope of the present disclosure fully encompasses otherembodiments which may become obvious to those skilled in the art, andthat the scope of the present disclosure is accordingly to be limited bynothing other than the appended claims, in which reference to an elementin the singular is not intended to mean “one and only one” unlessexplicitly so stated, but rather “one or more.” All structural,chemical, and functional equivalents to the elements of theabove-described preferred embodiment(s) that are known to those ofordinary skill in the art are expressly incorporated herein by referenceand are intended to be encompassed by the present claims. Moreover, itis not necessary for a device or method to address each and everyproblem sought to be solved by the present disclosure, for it to beencompassed by the present claims. Furthermore, no element, component,or method step in the present disclosure is intended to be dedicated tothe public regardless of whether the element, component, or method stepis explicitly recited in the claims.

1-40. (canceled)
 41. A compliant printed flexible circuit comprising: aflexible polymeric film; at least one dielectric layer selectivelyprinted on the polymeric film with recesses corresponding to a targetcircuit geometry; a conductive material printed in at least a portion ofthe recesses comprising a circuit geometry; at least one dielectriccovering layer printed over the conductive material; and at least oneopening in the dielectric covering layer providing access to at least aportion of the circuit geometry.
 42. The compliant printed flexiblecircuit of claim 41 comprising a conductive plating layer on at least aportion of the circuit geometry.
 43. The compliant printed flexiblecircuit of claim 41 wherein the conductive material comprises one ofsintered conductive particles or a conductive ink.
 44. The compliantprinted flexible circuit of claim 41 comprising a compliant materiallocated between the polymeric film and at least a portion of the circuitgeometry.
 45. The compliant printed flexible circuit of claim 41comprising a compliant material generally aligned with the opening inthe dielectric layer and positioned between the polymeric film and atleast a portion of the circuit geometry.
 46. The compliant printedflexible circuit of claim 41 comprising at least one printed electricaldevice on one of a dielectric layer or the polymeric film andelectrically coupled to at least a portion of the circuit geometry. 47.The compliant printed flexible circuit of claim 41 comprising an opticalquality material deposited in at least a portion of the recessescomprising one or more optical circuit geometries.
 48. The compliantprinted flexible circuit of claim 41 comprising one or more opticalfibers located in at least a portion of the recesses comprising one ormore optical circuit geometries.
 49. The compliant printed flexiblecircuit of claim 41 wherein at least a portion of the circuit geometrycomprises a via electrically coupling adjacent layers of the circuitgeometry.
 50. The compliant printed flexible circuit of claim 41comprising one or more contact members electrically coupled to at leasta portion of the circuit geometry and extending above the dielectriccovering layer.
 51. The compliant printed flexible circuit of claim 50wherein the compliant printed flexible circuit is singulated adjacent atleast one of the contact members.
 52. The compliant printed flexiblecircuit of claim 41 comprising: at least one contact member extendingalong a first surface of the compliant printed flexible circuit; and atleast one printed compliant member located on a second surface of thecompliant printed flexible circuit opposite at least one of the contactmembers.
 53. The compliant printed flexible circuit of claim 41 whereinconductive traces in the circuit geometry comprise substantiallyrectangular cross-sectional shapes.
 54. The compliant printed flexiblecircuit of claim 41 wherein a conductive material, a non-conductivematerial, and a semi-conductive material are printed on a single layer.55. An edge connector on the compliant printed flexible circuit of claim41 comprising: a first portion of the circuit geometry extending beyondthe dielectric covering layer; a compliant material located along asurface of the first portion of the circuit geometry; and a secondportion of the circuit geometry located on top of the compliantmaterial.
 56. An electrical interconnect assembly comprising: a housingretaining the compliant printed flexible circuit of claim 41; a firstcircuit member comprising electrical contacts compressively engaged withcontact members located along a first surface of the compliant printedflexible circuit; and a second circuit member comprising electricalcontacts compressively engaged with contact members located along asecond surface of the compliant printed flexible circuit.
 57. Theelectrical interconnect assembly of claim 56 wherein the first andsecond circuit members are selected from one of a dielectric layer, aprinted circuit board, a flexible circuit, a bare die device, anintegrated circuit device, organic or inorganic substrates, or a rigidcircuit.
 58. The compliant printed flexible circuit of claim 41comprising: at least one opening extending through the compliant printedflexible circuit; and at least one contact member inserted in theopening and electrically coupled to at least a portion of the circuitgeometry.
 59. A method of making a compliant printed flexible circuitcomprising: selectively printing at least one dielectric layer to aflexible polymeric film to create recesses corresponding to a targetcircuit geometry; printing a conductive material in at least a portionof the recesses comprising a circuit geometry; and printing at least onedielectric covering layer over at least the circuit geometry.
 60. Themethod of claim 59 comprising printing the dielectric covering layerwith at least one opening that provides access to at least a portion ofthe circuit geometry.
 61. The method of claim 59 comprising plating aconductive material on at least a portion of the circuit geometry. 62.The method of claim 59 wherein printing the conductive materialcomprises: printing a conductive material in the recesses; and sinteringthe conductive material.
 63. The method of claim 59 wherein printing theconductive material comprises printing a conductive ink in the recesses.64. The method of claim 59 comprising printing a compliant material in alocation between the polymeric film and at least a portion of thecircuit geometry.
 65. The method of claim 64 comprising aligning theprinted compliant material with an opening in the dielectric coveringlayer.
 66. The method of claim 59 comprising: printing at least oneelectrical device on one of a dielectric layer or the polymeric film;and electrically coupled the electrical device to at least a portion ofthe circuit geometry.
 67. The method of claim 59 comprising printing anoptical quality material in at least a portion of the recessescomprising one or more optical circuit geometries.
 68. The method ofclaim 59 comprising locating one or more optical fibers in at least aportion of the recesses comprising one or more optical circuitgeometries.
 69. The method of claim 59 comprising printing at least onevia in a dielectric layer to electrically couple adjacent layers of thecircuit geometry.
 70. The method of claim 59 comprising printing one ormore contact members that extends above the dielectric covering layerand electrically couple to at least a portion of the circuit geometry.71. The method of claim 70 comprising singulating at least a portion ofthe compliant printed flexible circuit adjacent at least one of thecontact members.
 72. The method of claim 59 comprising: printing one ormore contact members that extend above a first surface of the compliantprinted flexible circuit and electrically couple to at least a portionof the circuit geometry; and printing at least one compliant member on asecond surface of the compliant printed flexible circuit opposite atleast one of the contact members.
 73. The method of claim 59 whereinconductive traces in the circuit geometry comprise substantiallyrectangular cross-sectional shapes.
 74. The method of claim 59comprising printing a conductive material, a non-conductive material,and a semi-conductive material is printed on a single layer.
 75. Themethod of claim 59 comprising the steps of: locating pre-formedconductive trace materials in the recesses; and plating the recesses toform conductive traces with substantially rectangular cross-sectionalshapes.
 76. The method of claim 59 comprising the steps of: pressing aconductive foil into at least a portion of the recesses; shearing theconductive foil along edges of the recesses; removing excess conductivefoil not located in the recesses; and plating the recesses to formconductive traces with substantially rectangular cross-sectional shapes.77. A method of making an edge connector for a compliant printedflexible circuit made according to claim 59 comprising the steps of:printing a first portion of the circuit geometry beyond the dielectriccovering layer; printing a compliant material along a surface of thefirst portion of the circuit geometry; and printing a second portion ofthe circuit geometry on top of the compliant material.
 78. A method ofmaking an electrical interconnect assembly comprising the steps of:retaining a compliant printed flexible circuit made according to themethod of claim 59 in a housing; compressively coupling electricalcontacts on a first circuit member with contact members located along afirst surface of the compliant printed flexible circuit; andcompressively coupling electrical contacts on a second circuit memberwith contact members located along a second surface of the compliantprinted flexible circuit.
 79. The method of claim 78 wherein the firstand second circuit members are selected from one of a dielectric layer,a printed circuit board, a flexible circuit, a bare die device, anintegrated circuit device, organic or inorganic substrates, or a rigidcircuit.
 80. The method of claim 59 comprising the steps of: printing atleast one opening extending through the compliant printed flexiblecircuit; and inserting at least one contact member into the opening andelectrically coupling the contact member with at least a portion of thecircuit geometry.